Aqueous slurries of lime, or slaked lime, have many uses where relatively low amounts are required. Such uses include processes for water treatment, removal of contaminants from gaseous streams, and other processing where a continuous supply of slaked lime is required during periods of operation of such processes. Problems exist in the preparation of such slaked lime in that often grit or solids remain after slaking which, unless removed from the slaked lime, can cause clogging of equipment or other problems. For example, where the slaked lime is not continuously removed from a slaking apparatus and grit in a slaked lime is returned to a slaking unit, the grit may accumulate in the slaking unit and cause wear on slaking unit components, clogging of component conduits, and other problems. Also, although the slaking of lime is a exothermic reaction, when relatively small amounts of lime are to be slaked, the exotherm is not sufficient to maintain the desired temperature for slaking and heat must be added to effect a sufficient rate of slaking, which addition of heat is a cost factor that must be accommodated. Thus, due to the problem of heat of reaction, grit buildup, and other factors, the adequate slaking of relatively low amounts of lime has been a constant problem.
It is an object of the present invention to provide a lime slaking apparatus which can be used to continuously slake lime at a relatively low rate, for example, a rate of about 50 to 750 pounds per hour or less, with removal of grit from the slaked lime prior to return of slaked lime, for additional slaking, to the slaking vessel, which reduces wear on the slaker components, clogging and other problems associated with conventional slakers.
It is another object of the present invention to provide a lime slaking apparatus which can be used to continuously slake lime where the heat of an initially slaked supply of lime is used to provide heat to fresh lime slurry being slaked.
It is a further object of the present invention to provide for three different stages of mixing and slaking of lime by use of an inner slaking chamber, outer slaking chamber and recirculating pump device so as to provide improved slaking of lime in water.